Struct Superblock 

pub struct Superblock {
    pub magic: u64,
    pub version: u32,
    pub page_size: u32,
    pub wal_start_page: u32,
    pub wal_head_page: u32,
    pub tick_seq: u64,
    pub epoch_ms: i64,
}

Superblock, as it lives in the first SUPERBLOCK_BYTES bytes of page 0.

tick_seq is a publish sequence number, not a timestamp: it counts publishes from 1 upwards, so two ticks in the same millisecond still get distinct values. epoch_ms stays for the “when was this last touched” question, which is a wall-clock question and is answered by the clock.

Fields

magic: u64

version: u32

page_size: u32

wal_start_page: u32

wal_head_page: u32

tick_seq: u64

epoch_ms: i64

Implementations

impl Superblock

pub fn new() -> Self

pub fn to_payload(&self) -> [u8; 56]

The published payload. Byte 56..64 of the page is the seqlock counter and is deliberately not part of it, so a rewrite of the payload can never clear the counter out from under a reader.

pub fn from_payload(buf: &[u8]) -> Option<Self>

None when the page is not a superblock at all. A version other than the current one is still decoded: magic says whose file this is and the reader decides what to do with the older fields.

Trait Implementations

impl Clone for Superblock

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Superblock

impl Debug for Superblock

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Superblock

fn default() -> Self

Returns the “default value” for a type.